Looking for help regarding AHCI vs IDE

[jboydgolfer]

Hello,

I was recently given some New in Box,Western Digital Caviar Blue HDD'S.
I will be re-installing my win 7 after Some Deep PC cleaning.
I have some question's in regard's to AHCI/IDE storage setting's.
First off, which if either is better? I DO know that AHCI is a newer technology, but I am unaware of it's benefit's.
Is it different from IDE installation? I would assume it's the Same, but I am Mostly NEVER right.
Lastly, What EXACTLY is raid? I feel like an ass , having to ask this, but I'd like to know. I DO know what it is in a physical sense, but I Don't know what it is on a Software level , or what it's benefit's are.

Any and ALL help would be greatly appreciated.
If not, then Thanks for looking.

[brandonwh64]

How many have you received? I have two 500GB Blue drives in raid 0 and its quite peppy for mid level platter drives.

[jboydgolfer]

I was given 4, but I was only planning on keeping 2, mostly because a friend is in need of a reliable HDD, and I thought it would be good to spread the good fortune, by not being greedy. They are 250Gb/each.

[lilhasselhoffer]

Short answers.

Unless you're still using PATA HDDs you should be using AHCI.


Longer answer:
AHCI (Advanced Host Controller Interface) is the newer formalized communication protocol for HDDs and SSDs. It is more efficient than IDE (read - faster), and it enables RAID. IDE did/does not support RAID.


RAID is fun. There are two different versions, software and hardware. Software RAID allows a controller built into the motherboard to divide data up, and write it to the drives as if it were multiple separate data streams. Because the division and tracking takes some resources, some of the raw IO rate for the HDDs is lost to overhead. Additionally, if power is lost during a read/write the data is corrupted.

Hardware RAID utilizes a separate controller (ideally with its own power backup). The hardware solution utilizes specifically designed circuits to control data flow, so that less performance is lost (compared to software) in overhead. The backup power prevents data corruption from power loss.


The reality here is that very few people need hardware RAID, because of cost prohibitions. Let's say you've got 2 drives in RAID 0 (striped array). The raw performance of each drive is 100 Mb/s. Theoretically, you can get 200 Mb/s in RAID. The software RAID might actually be 170 Mb/s, whereas the hardware RAID might be 182 Mb/s (85% versus 91% efficiency). The problem is that a decent hardware RAID solution could cost another $150 (minimum). The extra 6% performance is generally not worth the extra money (to average consumers).

So, the hardware solution has never taken off on the consumer side. The initial cost disparity has become larger, as Intel and AMD now both incorporate RAID controllers into their chipsets. The lack of financial sense compounds, so the cost of hardware RAID solutions generally stagnated. The cycle repeats, and hardware RAID looks just as cost prohibitive as it did five years ago. People who need every bit of performance from their systems (read: data centers) purchase the hardware version, but this isn't enough purchasing to push for a decrease in pricing.


Sorry, off on a tangent for a moment there.

[Sasqui]

I asked the same question in a thread a few months back.

Whatever you do, ditch IDE

From all the input, RAID is the fastest. I'm still not clear what benefits there are of AHCI vs. RAID... from what I understand AHCI supports RAID.

When configured as RAID or ACHI, you can run drives in single or in a RAID array

XP does not provide native support for RAID, so you need to load drivers for RAID. Win7 has native drivers. I think ACHi is supported by XP - can someone confirm this???

Edit: Read this article too: http://www.differencebetween.net/tec...ahci-and-raid/
I think I'm wrong about AHCI allowing discs to be "RAIDed"

[brandonwh64]

Originally Posted by jboydgolfer

I was given 4, but I was only planning on keeping 2, mostly because a friend is in need of a reliable HDD, and I thought it would be good to spread the good fortune, by not being greedy. They are 250Gb/each.

Yea then what I would do is setup a Raid 0 with those two and enjoy the extra speed. Make sure you keep important information off of it in the even of failure.

[lilhasselhoffer]

Originally Posted by Sasqui

I asked the same question in a thread a few months back.

Whatever you do, ditch IDE

From all the input, RAID is the fastest. I'm still not clear what benefits there are of AHCI vs. RAID... from what I understand AHCI supports RAID.

When configured as RAID or ACHI, you can run drives in single or in a RAID array

XP does not provide native support for RAID, so you need to load drivers for RAID. Win7 has native drivers. I think ACHi is supported by XP - can someone confirm this???

Edit: Read this article too: http://www.differencebetween.net/tec...ahci-and-raid/
I think I'm wrong about AHCI allowing discs to be "RAIDed"

IDE doesn't have the faculties to do RAID.

AHCI is necessary for RAID, but RAID isn't necessary on AHCI. I've got a system that runs AHCI with 4 2TB discs as storage and 1 500 GB disk as the OS.

XP doesn't have AHCI support baked in. Vista, 7, and 8 do. You can add AHCI drivers into windows XP, but it is a chore.

AHCI and RAID options on a motherboard are splitting hairs. AHCI technically allows RAID, but often introduced compatibility issues in some drives. In order to address this some vendors have AHCI, RAID, and IDE modes to allow everything to work. RAID mode will do everything AHCI does. AHCI lacks proper RAID support, but it will work with almost any drive. IDE works with all drives, but doesn't do RAID.




All summed up: Run in at least AHCI mode (RAID if you can do a bit of troubleshooting and have more recent hardware). IDE is functionally dead, and it should be. Finally, RAID is a topic in and of itself. If you have questions on it I suggest you open another topic. There are more knowledgeable people than I on getting the best performance out of an array.

[Wrigleyvillain]

Firstly, go read the first parts of the wikipedia page on RAID.

Bottom line...go RAID 0 with two drives (or four if you decide to keep all) if you want speed plus have one single, "bigger" volume that is a combination of all the drives (two 250GB drives = one 500GB RAID 0 volume). But be aware that RAID0 is dangerous because it heightens the chances of data loss if a drive dies because only one has to have an issue for everything to be gone. So, for example, if you chose to go RAID 0 with all four you would have a pretty speedy 1TB volume there but are also then 4 times as likely to lose your data as running just one of those alone.

But, if you make regular backups like all with important data should no matter what, then no worries.

Regardless you definitely want to use AHCI mode and, also, there are ways to "span" volumes in Windows if you wanted.

[Sasqui]

Originally Posted by lilhasselhoffer

AHCI and RAID options on a motherboard are splitting hairs. AHCI technically allows RAID, but often introduced compatibility issues in some drives. In order to address this some vendors have AHCI, RAID, and IDE modes to allow everything to work. RAID mode will do everything AHCI does. AHCI lacks proper RAID support, but it will work with almost any drive. IDE works with all drives, but doesn't do RAID.

Good summary. The article I linked talked about AHCI being a subset of RAID.

The only drawback of setting up a single drive as RAID would be possible compability, correct? And that can be overcome with drivers.

Both AHCI and RAID support "hot swapping" from what I've read, while IDE does not.

[Wrigleyvillain]

Well I have my onboard controller set to RAID on my server box and any drives I don't add to an array just seem to work the same as if was set to AHCI.

As for hot swap yeah IDE mode does not support but the main reason as far as I know is that PATA drives do not physically support it. SATA and SAS power connectors are designed so that the "live" 12v pin makes contact before all the other ones (it's longer I believe). So hot swapping while using a SATA to molex adapter is dangerous as hell, for the record.

If I don't have all my facts straight here let me know.